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Video: Origami Diagramming 1

Edited by Linda Yau

This is the first in a series of video tutorials on drawing origami diagrams. The videos are hosted on YouTube, with articles here on The Fold to compliment the tutorials with text and downloadable content. This first video focuses on the basics of creating line drawings precisely in Inkscape, a free open source vector drawing program. I go over the basics of the different ways to produce drawings on a computer, get familiar with Inkscape, and then draw our first crease pattern. Watch below, with companion files and reference text below. Happy diagramming!

-Jason Ku



Example Files

Raster vs. Vector Graphics

There are two types of graphics on a computer. The first is called raster graphics and is good for manipulating photographs and images at fixed sizes. Images are produced by specifying a color at each point on a pixel grid, and can be created and modified using programs like Microsoft Paint and Adobe Photoshop. However, such images look bad when scaled up (they are not scalable) and making changes requires you to change each pixel one by one.

Vector graphics, on the other hand, are both scalable and easy to modify. Instead of representing a line as a bunch of black pixels on a white background, for vector graphics we represent a line by the location of its endpoints. We don't really care how the computer interprets these vector locations. We just care that when we draw a line we can easily move it and manipulate its style, color, etc.

While there is a lot of software for producing vector graphics, there are two that stand out. The first is Adobe Illustrator. Illustrator is the industry standard, full of features, but pretty expensive. Currently, a single app license for Illustrator costs about $20 per month. The second is Inkscape. Inkscape is open-source and freely available. It doesn't have all the features of Illustrator, but it is improving every year. I'm going to try to look at both Illustrator and Inkscape in this series, but we'll be starting with Inkscape since it is free.

Now, if you look on YouTube, there are already some videos on using Inkscape to draw origami diagrams, and many more tutorials on using Inkscape itself. While I will give a brief introduction to the software, I am going to focus on the features that I find most useful for drawing origami related diagrams, sharing some tricks and best practices that I've developed over the years.

Getting to Know Inkscape

First, we will need to download Inkscape from inkscape.org by choosing the appropriate operating system page in the Download menu. I'm using a Mac, so I choose the Mac OS X option. In this tutorial, we'll use Inkscape 0.91, which is the same version across all desktop platforms. Apple users will also need to download and install XQuarz which is the windowing system that Inkscape runs in.

After completing the installation on your machine, go ahead and open Inkscape. The first time you open Inkscape it may take a while to load while it configures initial preferences. Once it opens, you'll see the Inkscape environment. We will be drawing on pages located on what is called the canvas in the center of the view.

Around the canvas are useful menus and toolbars. Most commands can be accessed through the menu bar. The command bar houses shortcuts to the most common global actions. The tool box on the left holds the different tools you will use to draw and manipulate graphics. When a tool is selected, special tool specific shortcuts are available in the tool controls bar. On the right is the snap bar for configuring snap preferences. And on the bottom is the color palette and status bar. There are a lot of options, but don't worry about them for right now.

Before we even start drawing, there are a few preference that we'll want to change that to help with diagramming. Inkscape has two types of preferences: preferences associated with the application, and preferences associated with the document. First, let's modify the application preferences by going to Edit/Preferences, or by pressing the rightmost icon in the command bar. We're just going to make four small changes here.

First, under the Tool category, change the bounding box from "visual" to "geometric". The bounding box outlines the extent of a selected object. A geometric bounding box references the underlying geometry instead of object styles like stroke width.

Next, under the Node category, and select "Always show outline". Showing outlines will make it easier to see selected geometry.

Next, under Behavior choose the Transforms category, and deselect "Scale stroke width". When diagramming, we'll want to use standard stroke widths, so when we transform objects, we won't want those stroke widths to change.

Lastly, under the Steps category, and change the Rotation snaps to every 22.5 degrees. This is typically the most convenient setting for origami.

That's all we need to change here, so close that and open the document properties under the File menu or by clicking the second to last command bar icon. Notice that pixels are the default unit in Inkscape. There are 90 Inkscape pixels in one inch, but be careful. Other programs use a different default pixel sizes. Illustrator for example uses 72 pixels per inch.

I'll be diagramming for an American publication, so I'll change my page size to US Letter. The last option to change is under the Snaps menus. Here, adjust the snap distance to 5. This will allow us to be more precise when using snaps. Snapping is really useful when drawing origami diagrams. Let's close out of the document properties and turn on snaps. I've turned on all the snap options except for the ones involving bounding boxes.

Tool Box

Now in order to start drawing, let's take a look at the Tool Box. There are a lot of tools here, but for right now, we'll only need six of them. The Selector is the primary tool for moving and transforming objects. The Node is used for manipulating endpoints. The Zoom is used for navigation. The Ellipse tool is used for drawing circles. And the Pen tool is used for making straight and curved lines.

These tools are so useful, we will want to be able to change between them quickly using keyboard shortcuts. Press spacebar to access the Selector tool, press 'N' to access the Node tool, press 'Z' to access the Zoom tool, press 'E' to access the Ellipse tool, and press 'B' to access the Pen tool. (Why 'B'? The pen is really called the Bezier tool, but I digress). You can find a full list of keyboard shortcuts on the Inkscape website, here.

We'll start be making sure we can navigate around the canvas. To pan around the canvas, you can obviously use the scroll bars or possibly trackpad gestures, but the easiest way is to press and hold spacebar and move your mouse. To zoom in and out, use the Zoom tool. Click to zoom and shift click to zoom out. You can also click and drag an area to zoom to the selection. There are many keyboard shortcuts for standard zooms, such as zooming to the page by pressing '5'.

Drawing Lines

Now let's start drawing. The Pen will be our drawing tool of choice for pretty much everything. Let's start by selecting the Pen tool and clicking on the canvas. Clicking around creates a chain of line segments. To end the chain, just double click.

Now let's modify the chain. We can see its bounding box which means the chain is selected. To move the chain use the selector tool and press and drag. We can move the nodes of the chain individually by using the Node tool. While we can access the Node tool by pressing 'N', we can also access it by double clicking the chain with the Selector tool. The cursor changes and the nodes of the chain are highlighted. Click and drag to modify the chain.

Much of the time, we won't want our line segments to be connected since we might want to give each segment a different style. So let's get rid of the chain by selecting the chain and pressing delete.

To demonstrate some key aspects of drawing in Inkscape, we will draw the full crease pattern for a traditional crane. We'll start by drawing a square. We will do this by constructing four equal line segments at right angles to one another. First, we'll draw one of the horizontal sides. With the Pen tool, click one endpoint somewhere. If we hold down the Control key, we will notice that the line is constrained to multiples of 22.5 degrees, ensuring that we are drawing lines at the correct angles. Holding down the Control key, double click to the right to complete the segment. One side done!

We will construct the remaining three sides by transforming copies of this segment. With the segment selected, we can copy and paste objects by pressing Control-C and Control-V respectively. However, most of the time, we will want to just duplicate geometry, which we can do by pressing Control-D. Move the copy away from the original, and then rotate it 90 degrees by clicking either rotate icon in the Selector tool control bar. Then drag it to the right of the other segment until it snaps.

Snapping is really precise. If we zoom in on the connection, it looks like the two lines meet up well, though the line strokes make it difficult to be sure. When we only want to look at the underlying geometry of our drawing and ignore line styles, we can switch over to outline view. Click View/Display Mode/Outline. The line styles go away, and we see that in fact the lines match up perfectly. Outline mode can be great for checking the precision of your drawing, but we will stay in Normal mode most of the time. We can continue the same process to construct the last remaining two sides, duplicating, rotating, and then snapping. Square complete!

Now let's draw a bird base inside this square. First we draw the diagonals by snapping to the corners. Then we draw the horizontal and vertical halves by snapping to midpoints, holding down the Control key to make sure the lines are perpendicular. The petal fold crease lines are easily drawn, also by holding down the Control key. We can actually draw two of these diagonal lines at once, but these segment will be connected. We can separate this chain into two segments by selecting the middle node with the Node tool, and breaking the path at the selected node. Now they are separate lines, but they are still in the same path. We can break them apart by choosing 'Break Apart' in the Path menu. We don't have to draw the rest of the creases since they are the same as the ones we just drew. We can instead duplicate and rotate the existing creases and snap them into place.

This is a bird base crease pattern with all four corners folded together. To fold a crane, two flaps are folded up to form the wings. We can use the node tool to modify the creases. Folding the traditional crane further thins the head and tail by bisecting those flaps with a kite fold. I'll talk about two good methods for accurately constructing angle bisectors using Inkscape.

Bisecting Angles

Both methods involve constructing an isosceles triangle from the angle. We construct a circle centered at the angle's vertex using the Ellipse tool. Click on the vertex while holding down Shift and Control. Shift tells the ellipse to be centered at the starting click, while Control forces the ellipse into a circle. It is important that the circle intersect the two sides of the angle being divided.

The circle we just drew has a red fill color which is a little distracting. We can change the visual style of objects using the Fill & Stroke Dialog, accessible from the Object menu or the Command Bar. This Dialog will be useful for changing stroke widths and dash types later on, but for now, we will just remove the fill on this circle by pressing the X.

With our circle in place, we will draw a line between the circle's intersection points. Rotating this line 90 degrees splits the angle in half along its angle bisector. Now we would like the line to extend further than it does, and we can use the Selector tool to scale it appropriately. But when we scale the segment, we will want to keep its stroke width the same, thus we will turn off stroke width scaling in the Selector's tool control bar. Selecting the bisector, we can expand it along the same line by dragging a corner while holding down the Control key, using snapping to guide its final location.

Alternatively, we do not need to use the Ellipse tool at all. Instead we can simply duplication and rotate the angle's shorter side onto the other. To rotate about a specified axis, we select the side with the Selector tool, and click on it again. This will change the corner icons to rotation arrows, with a crosshair at the center. Drag the cross hair to the angle's vertex, and then drag a rotation arrow until the side snaps onto the other. Using the node tool to move the vertex endpoint to the starting location, and rotating by 90 degrees also results in an angle bisector. Duplicating, reflecting, and trimming finishes one quadrant.

We can duplicate these creases faster by grouping them by pressing Control-G while they are selected. Groups stay together until they are ungrouped by pressing Shift-Control-G. Duplication, rotation, and reflection complete the remaining sides.

Now for the reverse folds. The position and angle of the reverse folds for the head and the tail of the crane may be different from person to person. But for any angle, the creases corresponding the reverse folds will reflect across existing creases in the crease pattern. Like angle bisection, reflection is another common procedure in origami diagramming. We'll look at two different ways for reflecting lines.

Reflecting Lines

Let's concentrate on the head reverse fold. We can mark the reverse fold as an arbitrary line crossing one of the layers which will also be folded through all the other layers. All we need to do is reflect this line across each existing crease. To reflect a single segment using the first method, duplicate the reflection line and rotate it 90 degrees, snapping one end to the segment we want to reflect. Construct a segment to the reflection line, duplicate it, and reconstruct the reflection.

Alternatively, to reflect more objects, duplicate them in a group along with the reflection axis. Mirror it using a Selector shortcut, snap the ends of the reflection line together, and rotate until the lie on top of each other. A few more reflection, and the crease pattern is complete. Using snaps and careful transformations allow diagrams to be quite precise. Again, we can check the precision of our drawing in Outline mode.

This concludes our first tutorial on vector drawing for origami. Knowing how to draw lines accurately is the foundation of drawing origami crease patterns. Join me next time where we will focus on line styles and drawing origami diagrams with multiple layers.